In my above noted parent co-pending application, a filter apparatus is disclosed wherein an inclined movable belt or conveyor is utilized to support a continuous strip of filter media. For certain filtering applications it may be desirable to provide an apparatus that utilizes a movable continuous strip of filter media which does not require a belt or conveyor to support the media. In such an apparatus the media from a suitable supply roll is supported on a fixed structure and pulled by a suitable means capable of gripping the front or free end of the media. The filter media forms the bottom of a receiving tank for dirty liquid to be filtered and directly below it is a collection tank for clean liquid. A suction pump attached to an outlet from the collection tank creates a reduced pressure in the collection tank which increases the flow of liquid from the receiving tank through the media. When the suction pump is in operation, the reduced pressure created thereby in the collection tank causes the filter media to cling tightly to its supporting grill and in this position the media continues to trap more and and more filtrate on its upper surface. As filtered out material from the dirty liquid continues to build up on the filter media the pressure in the collection tank becomes progressively less, as well as the flow of liquid through the media. It thus becomes necessary to advance the media to provide fresh, unloaded filter media. However, in an apparatus with no belt or conveyor, movement of the loaded media becomes difficult, if not impossible, if the pressure differential between the receiving and collection tanks is relatively high, that is, if the pressure in the collection tank remains substantially lower from that in the receiving tank. Thus, it became essential to provide a solution to this problem of equalizing the pressure in the receiving and collection tanks just prior to movement of the filter media.